When Database Queries are Fourth Amendment Searches

Due to limits on the scope of the Fourth Amendment and numerous exceptions to its warrant requirement, Fourth Amendment doctrine permits the government to collect a great deal of information about Americans with limited constitutional constraints. Both courts and commentators have recognized that this vast collection authority raises significant privacy concerns. The conventional response has been to suggest various modifications to the existing information-collection rules. Data collection, however, is only one part of the problem. The government’s post-collection use of information alone can—and often does—have equally disturbing privacy implications. The most troubling example has been labeled the “aggregation problem.” The aggregation and analysis of data in the government’s possession actually can result in revelations that could not have been gleaned from viewing those data in isolation. This article argues that, as a result, collection-focused solutions to privacy concerns—while valuable—are alone insufficient. They must be supplemented by rules regarding the government’s use of information. Where broad collection authority combines with the capacity to aggregate data in ways that reveal new information, the extraction of that information should be subject to constitutionally based limits. Specifically, this article focuses on one such extraction tool: database “queries.” When queries about U.S. persons are reasonably likely to expose knowledge about those individuals discoverable only by aggregating multiple pieces of data, such queries should be considered searches regulated by the Fourth Amendment. Both the purpose of the Fourth Amendment and the intrusive nature of the information that such queries can reveal support this conclusion. And while such an expansion of Fourth Amendment doctrine is no small undertaking, the Foreign Intelligence Surveillance Court’s oversight of government surveillance programs already provides a blueprint for how to implement this regulation.